The relative motion between two bodies may be used to generate electrical power and this technique has been used to power remote sensors such as waterway buoys. Waterway buoys range from simple channel marking devices to complex data gathering sensors that collect information such as wind speed, air temperature, water temperature, wave heights, and the like. For example, a simple channel marking device is illustrated in U.S. Pat. No. 4,423,334 to Jacobi et al. The Jacobi et al. patent discloses a spherical buoy carrying a battery and an arcuate member having two ends surrounded by magnetic loops. A body having two windings at its ends travels along the arcuate member in response to the buoy being moved by wave action. The movement of the body winding through a respective magnetic loop induces an electrical current that is used to recharge the battery.
An example of a buoy used as a complex data gathering sensor is a moored buoy in the National Data Buoy Center (NDBC) monitoring network. An NDBC buoy is part of a sensor network that is distributed throughout the U.S. waterways system to provide mariners with current and historical marine information. These buoys are typically powered by a combination of solar panels and storage batteries.
Another type of buoy that monitors the surrounding ocean conditions is the PowerBuoy™ distributed by Ocean Power Technologies, Inc. of Pennington, N.J. This buoy has a power generation system that includes a disc connected to a piston-like structure. The disc is free to rise and fall when exposed to wave action thereby actuating the piston-like structure, which drives a generator on the ocean floor for producing electricity.
U.S. Pat. No. 6,936,994 to Gimlan also discloses a buoy for generating power that includes a body coupled to a flywheel and a capacitor means. The body oscillates back and forth in the buoy in response to the buoy being moved by the water and such movement is translated by the flywheel and capacitor means to generate electrical energy.
U.S. Pat. No. 3,696,251 to Last et al. discloses a generator for deriving electrical energy from the oscillatory motion of a buoy using a single plane rocking pendulum. The generator includes a pendulum having a permanent magnet for the bob, and an arcuate member comprising a winding is positioned under the travel path of the bob. The interaction of the permanent magnet with the winding of the arcuate member generates electrical current.
There are also types of power generators that uses fluid movement to generate power such as U.S. Pat. No. 4,781,023 to Gordon, and U.S. Pat. No. 6,647,716 to Boyd. Each of these patents discloses a base anchored in a body of water. A float is connected to the base via a linkage member that translates the relative motion of the float in relation to the base into mechanical, hydraulic, or electrical power.
The relative motion between two bodies can also be used to generate electrical signals indicative of the movement between the two bodies. For instance, U.S. Pat. No. 4,344,004 to Okubo discloses a sensor for detecting the positioning of a spherical body having an electret on the surface. The sensor includes a base having a hemispherical recess therein with two electrically conductive regions. The spherical body moves on a dielectric in the hemispherical recess. The electrically conductive regions are connected to sensing circuitry that determine the positioning of the sphere based upon the interaction of the electret and the electrically conductive regions.
U.S. Pat. No. 5,450,049 also discloses a sensor for generating electrical signals indicative of the movement experienced by a body. The sensor includes a housing carrying a pendulum having a permanent magnet at the free end. Each end of a reed switch is connected to a circuit and the reed switch is positioned below the pendulum. The reed switch is responsive to the permanent magnet of the pendulum to thereby complete the circuit.
Unfortunately, the above described conventional systems may be inefficient at generating electrical power for self-powering applications for movements along multiple degrees of freedom, or for movement sensing systems.